SANTIAGO DE COMPOSTELA, Spain — Spanish royals and political leaders joined hundreds in Santiago de Compostela’s storied cathedral Monday evening to mourn the 79 people killed in last week’s train crash, as investigators prepared to examine the train’s ‘‘black box’’ data recorders for more clues into the country’s worst rail disaster in decades.

Driver Francisco Jose Garzon Amo faces multiple counts of negligent homicide for the tragedy. The investigation has increasingly focused on him and his failure to brake as the train hurtled into a high-risk curve.

The black box could clear up whether there was a mechanical or technical failure. Experts will start examining it Tuesday under the instruction of Judge Luis Alaez, a court spokeswoman said on condition of anonymity in keeping with court policy.